Classifications

• • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
  • F25—REFRIGERATION OR COOLING; COMBINED HEATING AND REFRIGERATION SYSTEMS; HEAT PUMP SYSTEMS; MANUFACTURE OR STORAGE OF ICE; LIQUEFACTION SOLIDIFICATION OF GASES
  • F25J—LIQUEFACTION, SOLIDIFICATION OR SEPARATION OF GASES OR GASEOUS OR LIQUEFIED GASEOUS MIXTURES BY PRESSURE AND COLD TREATMENT OR BY BRINGING THEM INTO THE SUPERCRITICAL STATE
  • F25J3/00—Processes or apparatus for separating the constituents of gaseous or liquefied gaseous mixtures involving the use of liquefaction or solidification
  • F25J3/02—Processes or apparatus for separating the constituents of gaseous or liquefied gaseous mixtures involving the use of liquefaction or solidification by rectification, i.e. by continuous interchange of heat and material between a vapour stream and a liquid stream
  • F25J3/04—Processes or apparatus for separating the constituents of gaseous or liquefied gaseous mixtures involving the use of liquefaction or solidification by rectification, i.e. by continuous interchange of heat and material between a vapour stream and a liquid stream for air
  • F25J3/04406—Processes or apparatus for separating the constituents of gaseous or liquefied gaseous mixtures involving the use of liquefaction or solidification by rectification, i.e. by continuous interchange of heat and material between a vapour stream and a liquid stream for air using a dual pressure main column system
  • F25J3/04412—Processes or apparatus for separating the constituents of gaseous or liquefied gaseous mixtures involving the use of liquefaction or solidification by rectification, i.e. by continuous interchange of heat and material between a vapour stream and a liquid stream for air using a dual pressure main column system in a classical double column flowsheet, i.e. with thermal coupling by a main reboiler-condenser in the bottom of low pressure respectively top of high pressure column
• • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
  • F25—REFRIGERATION OR COOLING; COMBINED HEATING AND REFRIGERATION SYSTEMS; HEAT PUMP SYSTEMS; MANUFACTURE OR STORAGE OF ICE; LIQUEFACTION SOLIDIFICATION OF GASES
  • F25J—LIQUEFACTION, SOLIDIFICATION OR SEPARATION OF GASES OR GASEOUS OR LIQUEFIED GASEOUS MIXTURES BY PRESSURE AND COLD TREATMENT OR BY BRINGING THEM INTO THE SUPERCRITICAL STATE
  • F25J3/00—Processes or apparatus for separating the constituents of gaseous or liquefied gaseous mixtures involving the use of liquefaction or solidification
  • F25J3/02—Processes or apparatus for separating the constituents of gaseous or liquefied gaseous mixtures involving the use of liquefaction or solidification by rectification, i.e. by continuous interchange of heat and material between a vapour stream and a liquid stream
  • F25J3/04—Processes or apparatus for separating the constituents of gaseous or liquefied gaseous mixtures involving the use of liquefaction or solidification by rectification, i.e. by continuous interchange of heat and material between a vapour stream and a liquid stream for air
  • F25J3/04006—Providing pressurised feed air or process streams within or from the air fractionation unit
  • F25J3/04078—Providing pressurised feed air or process streams within or from the air fractionation unit providing pressurized products by liquid compression and vaporisation with cold recovery, i.e. so-called internal compression
  • F25J3/0409—Providing pressurised feed air or process streams within or from the air fractionation unit providing pressurized products by liquid compression and vaporisation with cold recovery, i.e. so-called internal compression of oxygen
• • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
  • F25—REFRIGERATION OR COOLING; COMBINED HEATING AND REFRIGERATION SYSTEMS; HEAT PUMP SYSTEMS; MANUFACTURE OR STORAGE OF ICE; LIQUEFACTION SOLIDIFICATION OF GASES
  • F25J—LIQUEFACTION, SOLIDIFICATION OR SEPARATION OF GASES OR GASEOUS OR LIQUEFIED GASEOUS MIXTURES BY PRESSURE AND COLD TREATMENT OR BY BRINGING THEM INTO THE SUPERCRITICAL STATE
  • F25J3/00—Processes or apparatus for separating the constituents of gaseous or liquefied gaseous mixtures involving the use of liquefaction or solidification
  • F25J3/02—Processes or apparatus for separating the constituents of gaseous or liquefied gaseous mixtures involving the use of liquefaction or solidification by rectification, i.e. by continuous interchange of heat and material between a vapour stream and a liquid stream
  • F25J3/04—Processes or apparatus for separating the constituents of gaseous or liquefied gaseous mixtures involving the use of liquefaction or solidification by rectification, i.e. by continuous interchange of heat and material between a vapour stream and a liquid stream for air
  • F25J3/04151—Purification and (pre-)cooling of the feed air; recuperative heat-exchange with product streams
  • F25J3/04163—Hot end purification of the feed air
  • F25J3/04169—Hot end purification of the feed air by adsorption of the impurities
  • F25J3/04175—Hot end purification of the feed air by adsorption of the impurities at a pressure of substantially more than the highest pressure column
• • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
  • F25—REFRIGERATION OR COOLING; COMBINED HEATING AND REFRIGERATION SYSTEMS; HEAT PUMP SYSTEMS; MANUFACTURE OR STORAGE OF ICE; LIQUEFACTION SOLIDIFICATION OF GASES
  • F25J—LIQUEFACTION, SOLIDIFICATION OR SEPARATION OF GASES OR GASEOUS OR LIQUEFIED GASEOUS MIXTURES BY PRESSURE AND COLD TREATMENT OR BY BRINGING THEM INTO THE SUPERCRITICAL STATE
  • F25J3/00—Processes or apparatus for separating the constituents of gaseous or liquefied gaseous mixtures involving the use of liquefaction or solidification
  • F25J3/02—Processes or apparatus for separating the constituents of gaseous or liquefied gaseous mixtures involving the use of liquefaction or solidification by rectification, i.e. by continuous interchange of heat and material between a vapour stream and a liquid stream
  • F25J3/04—Processes or apparatus for separating the constituents of gaseous or liquefied gaseous mixtures involving the use of liquefaction or solidification by rectification, i.e. by continuous interchange of heat and material between a vapour stream and a liquid stream for air
  • F25J3/04151—Purification and (pre-)cooling of the feed air; recuperative heat-exchange with product streams
  • F25J3/04187—Cooling of the purified feed air by recuperative heat-exchange; Heat-exchange with product streams
  • F25J3/04218—Parallel arrangement of the main heat exchange line in cores having different functions, e.g. in low pressure and high pressure cores
  • F25J3/04224—Cores associated with a liquefaction or refrigeration cycle
• • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
  • F25—REFRIGERATION OR COOLING; COMBINED HEATING AND REFRIGERATION SYSTEMS; HEAT PUMP SYSTEMS; MANUFACTURE OR STORAGE OF ICE; LIQUEFACTION SOLIDIFICATION OF GASES
  • F25J—LIQUEFACTION, SOLIDIFICATION OR SEPARATION OF GASES OR GASEOUS OR LIQUEFIED GASEOUS MIXTURES BY PRESSURE AND COLD TREATMENT OR BY BRINGING THEM INTO THE SUPERCRITICAL STATE
  • F25J3/00—Processes or apparatus for separating the constituents of gaseous or liquefied gaseous mixtures involving the use of liquefaction or solidification
  • F25J3/02—Processes or apparatus for separating the constituents of gaseous or liquefied gaseous mixtures involving the use of liquefaction or solidification by rectification, i.e. by continuous interchange of heat and material between a vapour stream and a liquid stream
  • F25J3/04—Processes or apparatus for separating the constituents of gaseous or liquefied gaseous mixtures involving the use of liquefaction or solidification by rectification, i.e. by continuous interchange of heat and material between a vapour stream and a liquid stream for air
  • F25J3/04248—Generation of cold for compensating heat leaks or liquid production, e.g. by Joule-Thompson expansion
  • F25J3/04278—Generation of cold for compensating heat leaks or liquid production, e.g. by Joule-Thompson expansion using external refrigeration units, e.g. closed mechanical or regenerative refrigeration units
• • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
  • F25—REFRIGERATION OR COOLING; COMBINED HEATING AND REFRIGERATION SYSTEMS; HEAT PUMP SYSTEMS; MANUFACTURE OR STORAGE OF ICE; LIQUEFACTION SOLIDIFICATION OF GASES
  • F25J—LIQUEFACTION, SOLIDIFICATION OR SEPARATION OF GASES OR GASEOUS OR LIQUEFIED GASEOUS MIXTURES BY PRESSURE AND COLD TREATMENT OR BY BRINGING THEM INTO THE SUPERCRITICAL STATE
  • F25J3/00—Processes or apparatus for separating the constituents of gaseous or liquefied gaseous mixtures involving the use of liquefaction or solidification
  • F25J3/02—Processes or apparatus for separating the constituents of gaseous or liquefied gaseous mixtures involving the use of liquefaction or solidification by rectification, i.e. by continuous interchange of heat and material between a vapour stream and a liquid stream
  • F25J3/04—Processes or apparatus for separating the constituents of gaseous or liquefied gaseous mixtures involving the use of liquefaction or solidification by rectification, i.e. by continuous interchange of heat and material between a vapour stream and a liquid stream for air
  • F25J3/04248—Generation of cold for compensating heat leaks or liquid production, e.g. by Joule-Thompson expansion
  • F25J3/04284—Generation of cold for compensating heat leaks or liquid production, e.g. by Joule-Thompson expansion using internal refrigeration by open-loop gas work expansion, e.g. of intermediate or oxygen enriched (waste-)streams
  • F25J3/0429—Generation of cold for compensating heat leaks or liquid production, e.g. by Joule-Thompson expansion using internal refrigeration by open-loop gas work expansion, e.g. of intermediate or oxygen enriched (waste-)streams of feed air, e.g. used as waste or product air or expanded into an auxiliary column
  • F25J3/04296—Claude expansion, i.e. expanded into the main or high pressure column
• • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
  • F25—REFRIGERATION OR COOLING; COMBINED HEATING AND REFRIGERATION SYSTEMS; HEAT PUMP SYSTEMS; MANUFACTURE OR STORAGE OF ICE; LIQUEFACTION SOLIDIFICATION OF GASES
  • F25J—LIQUEFACTION, SOLIDIFICATION OR SEPARATION OF GASES OR GASEOUS OR LIQUEFIED GASEOUS MIXTURES BY PRESSURE AND COLD TREATMENT OR BY BRINGING THEM INTO THE SUPERCRITICAL STATE
  • F25J3/00—Processes or apparatus for separating the constituents of gaseous or liquefied gaseous mixtures involving the use of liquefaction or solidification
  • F25J3/02—Processes or apparatus for separating the constituents of gaseous or liquefied gaseous mixtures involving the use of liquefaction or solidification by rectification, i.e. by continuous interchange of heat and material between a vapour stream and a liquid stream
  • F25J3/04—Processes or apparatus for separating the constituents of gaseous or liquefied gaseous mixtures involving the use of liquefaction or solidification by rectification, i.e. by continuous interchange of heat and material between a vapour stream and a liquid stream for air
  • F25J3/04248—Generation of cold for compensating heat leaks or liquid production, e.g. by Joule-Thompson expansion
  • F25J3/04284—Generation of cold for compensating heat leaks or liquid production, e.g. by Joule-Thompson expansion using internal refrigeration by open-loop gas work expansion, e.g. of intermediate or oxygen enriched (waste-)streams
  • F25J3/0429—Generation of cold for compensating heat leaks or liquid production, e.g. by Joule-Thompson expansion using internal refrigeration by open-loop gas work expansion, e.g. of intermediate or oxygen enriched (waste-)streams of feed air, e.g. used as waste or product air or expanded into an auxiliary column
  • F25J3/04303—Lachmann expansion, i.e. expanded into oxygen producing or low pressure column
• • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
  • F25—REFRIGERATION OR COOLING; COMBINED HEATING AND REFRIGERATION SYSTEMS; HEAT PUMP SYSTEMS; MANUFACTURE OR STORAGE OF ICE; LIQUEFACTION SOLIDIFICATION OF GASES
  • F25J—LIQUEFACTION, SOLIDIFICATION OR SEPARATION OF GASES OR GASEOUS OR LIQUEFIED GASEOUS MIXTURES BY PRESSURE AND COLD TREATMENT OR BY BRINGING THEM INTO THE SUPERCRITICAL STATE
  • F25J3/00—Processes or apparatus for separating the constituents of gaseous or liquefied gaseous mixtures involving the use of liquefaction or solidification
  • F25J3/02—Processes or apparatus for separating the constituents of gaseous or liquefied gaseous mixtures involving the use of liquefaction or solidification by rectification, i.e. by continuous interchange of heat and material between a vapour stream and a liquid stream
  • F25J3/04—Processes or apparatus for separating the constituents of gaseous or liquefied gaseous mixtures involving the use of liquefaction or solidification by rectification, i.e. by continuous interchange of heat and material between a vapour stream and a liquid stream for air
  • F25J3/04248—Generation of cold for compensating heat leaks or liquid production, e.g. by Joule-Thompson expansion
  • F25J3/04375—Details relating to the work expansion, e.g. process parameter etc.
  • F25J3/04393—Details relating to the work expansion, e.g. process parameter etc. using multiple or multistage gas work expansion
• • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
  • F25—REFRIGERATION OR COOLING; COMBINED HEATING AND REFRIGERATION SYSTEMS; HEAT PUMP SYSTEMS; MANUFACTURE OR STORAGE OF ICE; LIQUEFACTION SOLIDIFICATION OF GASES
  • F25J—LIQUEFACTION, SOLIDIFICATION OR SEPARATION OF GASES OR GASEOUS OR LIQUEFIED GASEOUS MIXTURES BY PRESSURE AND COLD TREATMENT OR BY BRINGING THEM INTO THE SUPERCRITICAL STATE
  • F25J3/00—Processes or apparatus for separating the constituents of gaseous or liquefied gaseous mixtures involving the use of liquefaction or solidification
  • F25J3/02—Processes or apparatus for separating the constituents of gaseous or liquefied gaseous mixtures involving the use of liquefaction or solidification by rectification, i.e. by continuous interchange of heat and material between a vapour stream and a liquid stream
  • F25J3/04—Processes or apparatus for separating the constituents of gaseous or liquefied gaseous mixtures involving the use of liquefaction or solidification by rectification, i.e. by continuous interchange of heat and material between a vapour stream and a liquid stream for air
  • F25J3/04763—Start-up or control of the process; Details of the apparatus used
  • F25J3/04769—Operation, control and regulation of the process; Instrumentation within the process
  • F25J3/04812—Different modes, i.e. "runs" of operation
• • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
  • F25—REFRIGERATION OR COOLING; COMBINED HEATING AND REFRIGERATION SYSTEMS; HEAT PUMP SYSTEMS; MANUFACTURE OR STORAGE OF ICE; LIQUEFACTION SOLIDIFICATION OF GASES
  • F25J—LIQUEFACTION, SOLIDIFICATION OR SEPARATION OF GASES OR GASEOUS OR LIQUEFIED GASEOUS MIXTURES BY PRESSURE AND COLD TREATMENT OR BY BRINGING THEM INTO THE SUPERCRITICAL STATE
  • F25J2210/00—Processes characterised by the type or other details of the feed stream
  • F25J2210/06—Splitting of the feed stream, e.g. for treating or cooling in different ways
• • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
  • F25—REFRIGERATION OR COOLING; COMBINED HEATING AND REFRIGERATION SYSTEMS; HEAT PUMP SYSTEMS; MANUFACTURE OR STORAGE OF ICE; LIQUEFACTION SOLIDIFICATION OF GASES
  • F25J—LIQUEFACTION, SOLIDIFICATION OR SEPARATION OF GASES OR GASEOUS OR LIQUEFIED GASEOUS MIXTURES BY PRESSURE AND COLD TREATMENT OR BY BRINGING THEM INTO THE SUPERCRITICAL STATE
  • F25J2270/00—Refrigeration techniques used
  • F25J2270/14—External refrigeration with work-producing gas expansion loop
• • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
  • F25—REFRIGERATION OR COOLING; COMBINED HEATING AND REFRIGERATION SYSTEMS; HEAT PUMP SYSTEMS; MANUFACTURE OR STORAGE OF ICE; LIQUEFACTION SOLIDIFICATION OF GASES
  • F25J—LIQUEFACTION, SOLIDIFICATION OR SEPARATION OF GASES OR GASEOUS OR LIQUEFIED GASEOUS MIXTURES BY PRESSURE AND COLD TREATMENT OR BY BRINGING THEM INTO THE SUPERCRITICAL STATE
  • F25J2270/00—Refrigeration techniques used
  • F25J2270/40—Quasi-closed internal or closed external air refrigeration cycle
• • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
  • F25—REFRIGERATION OR COOLING; COMBINED HEATING AND REFRIGERATION SYSTEMS; HEAT PUMP SYSTEMS; MANUFACTURE OR STORAGE OF ICE; LIQUEFACTION SOLIDIFICATION OF GASES
  • F25J—LIQUEFACTION, SOLIDIFICATION OR SEPARATION OF GASES OR GASEOUS OR LIQUEFIED GASEOUS MIXTURES BY PRESSURE AND COLD TREATMENT OR BY BRINGING THEM INTO THE SUPERCRITICAL STATE
  • F25J2270/00—Refrigeration techniques used
  • F25J2270/90—External refrigeration, e.g. conventional closed-loop mechanical refrigeration unit using Freon or NH3, unspecified external refrigeration
  • F25J2270/902—Details about the refrigeration cycle used, e.g. composition of refrigerant, arrangement of compressors or cascade, make up sources, use of reflux exchangers etc.

Definitions

• the present invention relates to a method and system for cryogenic air separation involving production of liquid products by using a closed loop supplemental refrigeration circuit. More particularly, the present invention relates to a supplemental refrigeration circuit that can be easily tied-in to an existing air separation plant.
• Oxygen is separated from oxygen containing feeds, such as air, through cryogenic rectification.
• refrigeration In order to operate a cryogenic rectification plant, refrigeration must be supplied to offset ambient heat leakage, warm end heat exchange losses and to allow the extraction or production of liquid products, including liquid oxygen, liquid nitrogen, or liquid argon.
• the main source of refrigeration for a cryogenic rectification plant is typically supplied by expanding part of the feed air stream or a waste stream to generate a cold stream that is then introduced into the main heat exchanger or the distillation column
• external refrigeration can also be imparted by other refrigerant streams introduced into the main heat exchanger, including a refrigerant stream from a closed loop supplemental refrigeration cycles as described in U.S. Patent No. 8,397,535.
• centrifugal compressors and turbo- expanders in such supplemental refrigeration circuits involve additional capital costs that when operating, are generally operating in an On' or Off mode.
• the centrifugal compressors and turbo-expanders are either operating so as produce the supplemental refrigeration and additional liquid product make or are shut down thereby not producing supplemental refrigeration or foregoing any additional liquid product make.
• the continued cycling of the centrifugal compressors and turbo-expanders between operating mode and shut-down mode adversely impacts the overall efficiency and reliability of the supplemental refrigeration cycle.
• a small degree of adjustment in existing supplemental refrigeration circuits may be achieved through the adjustment of compressor inlet guide vanes.
• the present invention is a system and method for providing supplemental refrigeration to an air separation plant by means of a closed loop supplemental refrigeration circuit that can be easily retrofitted or added to an air separation plant at a later date to increase the liquid product production capability of the air separation plant.
• the supplemental refrigeration capacity of the supplemental refrigeration circuit is controlled by removing or adding a portion of the refrigerant in the supplemental refrigeration circuit to adjust the inlet pressure while maintaining a substantially constant volumetric flow rate and substantially constant pressure ratio across the compressor. Removing the refrigerant from the supplemental refrigeration circuit decreases the refrigeration imparted by the supplemental refrigeration circuit and thus provides the capacity to turn-down liquid product make without shutting down the compressors and turbo-expanders in the supplemental refrigeration circuit.
• the present invention may be characterized as a method of separating air comprising the steps of: (i) conducting a cryogenic rectification process in an air separation plant comprising a main heat exchanger to cool a compressed and purified feed air stream to a temperature suitable for the rectification of the feed air stream and a distillation column system configured to rectify the compressed, purified and cooled air to produce at least one liquid product stream; (ii) diverting a portion of the compressed and purified feed air stream as a working fluid to a supplemental
• the present invention may also be characterized as method of providing supplemental refrigeration to an air separation plant comprising the steps of: (i) diverting a portion of a compressed and purified feed air stream from the air separation plant as a working fluid to a supplemental refrigeration circuit; (ii) compressing the working fluid in a compressor section within the supplemental refrigeration circuit; (iii) expanding the working fluid in a turbo-expander disposed within the supplemental refrigeration circuit to produce a cooled working fluid; (iv) directing the cooled working fluid to an auxiliary heat exchanger and warming the cooled working fluid in the auxiliary heat exchanger via indirect heat exchange with a boosted compressed air stream diverted from the air separation plant; (v) recirculating the warmed working fluid to the compressor section within the supplemental refrigeration circuit after having passed through the auxiliary heat exchanger; and (vi) returning the cooled, boosted compressed air stream exiting the auxiliary heat exchanger to the air separation plant to impart a portion of the refrigeration required by the air separation plant.
• the present invention may be characterized as a
• supplemental refrigeration system comprising: (a) an intake conduit configured to be coupled to an air separation plant and receive a portion of a compressed and purified air stream from the air separation plant, wherein the portion of the compressed and purified air stream forms a working fluid; (b) a compressor section fluidically coupled to the intake conduit and configured to compress the working fluid; (c) a turbo-expander section operatively coupled to the compressor section and configured to expand the compressed working fluid to generate a cooled working fluid; (d) an auxiliary heat exchanger configured to be coupled to the air separation plant to receive a boosted compressed air stream from the air separation plant and return a cooled, boosted compressed air stream back to the air separation plant; (e) the auxiliary heat exchanger further configured to receive the cooled working fluid from the turbo-expander section and warm the cooled working fluid via indirect heat exchange with the boosted compressed air stream from the air separation plant to impart a portion of the refrigeration required by the air separation plant; and (f) a recirculating conduit configured to return the warmed working fluid from the
• the invention may also be characterized as an air separation plant configured to produce at least one liquid product stream, the air separation plant comprising: (a) an air intake circuit configured to compress and purify an incoming feed air stream; (b) a distillation column system configured to rectifying the compressed and purified feed air stream by a cryogenic rectification process to produce at least one liquid product stream; (c)a main heat exchanger operatively associated with the compressed and purified feed stream and distillation column system and configured to cool the compressed and purified feed stream to a temperature suitable for the rectification of the compressed and purified feed air stream; (d) a supplemental refrigeration circuit coupled to the main heat exchanger, the supplemental refrigeration circuit comprising: (dl) an intake conduit configured to receive a portion of a compressed and purified feed air stream from the air intake circuit wherein the portion of the compressed and purified feed air stream forms a working fluid; (d2) a compressor section fluidically coupled to the intake conduit and configured to compress the working fluid; (d3) a turbo-expander section
• FIG. 1 is a schematic process flow diagram of a cryogenic air separation plant integrated with an add-on supplemental refrigeration circuit in accordance with the present invention.
• Fig. 1 there is shown a simplified illustration of a cryogenic air separation plant 1.
• the cryogenic air separation plant 1 includes a main feed air compression train 2, a main or primary heat exchanger 3, a turbine based refrigeration circuit 4, and a distillation column system 5.
• Most cryogenic air separation plants may further include various booster air compression circuits 6 and optionally a closed loop supplemental refrigeration circuit 7.
• the cryogenic air separation plant 1 depicted in Fig. 1 includes an add-on supplemental refrigeration circuit 7 which is integrated with and designed to allow increase production of liquid products from the air separation plant 1 and allow turn-down of liquid product make when less liquid products are required in a manner that optimizes the overall air separation plant efficiency and costs.
• the incoming feed air 10 is compressed in a multi-stage, intercooled main air compressor arrangement 12 to a pressure that can be between about 5 bar(a) and about 15 bar(a).
• This main air compressor arrangement 12 may be an integrally geared compressor or a direct drive compressor.
• the compressed air feed 14 is then purified in a pre-purifi cation unit 16 to remove high boiling contaminants from the incoming feed air.
• a pre-purification unit 16 typically contains beds of alumina and/or molecular sieve operating in accordance with a temperature and/or pressure swing adsorption cycle in which moisture and other impurities, such as carbon dioxide, water vapor and
• hydrocarbons are adsorbed.
• the compressed, purified feed air stream 18 is separated into oxygen-rich, nitrogen-rich, and argon-rich fractions in a plurality of distillation columns including a higher pressure column 52, a lower pressure column 54, and optionally, argon column (not shown).
• the compressed, pre-purified feed air stream 18 is split into a plurality of feed air streams, including streams 20, 22 that are cooled to temperatures suitable for rectification.
• Cooling the compressed, purified feed air streams is accomplished by way of indirect heat exchange in main heat exchanger 3 with the warming streams which include the oxygen, nitrogen and/or argon streams from the distillation column system 5.
• Refrigeration is also typically generated by the cold and/or warm turbine arrangements disposed within the turbine based refrigeration circuits 4 and any optional closed loop warm refrigeration circuit 7.
• the compressed and purified feed air stream 18 is divided into a first stream 20, a second stream 22 and a third stream 110.
• First stream 20 is then further compressed within a booster compressor arrangement 23, of the booster air compression circuit 6, which preferably comprises another single or multi-stage intercooled compressor.
• this second compressor arrangement 23 may be an integrally geared compressor or a direct drive compressor.
• This second compressor arrangement 23 further compresses the first stream 20 to a pressure between about 25 bar(a) and about 70 bar(a) to produce a further compressed stream 24.
• the further compressed stream 24 is directed or introduced into main heat exchanger 3 where it is cooled and liquefied at the cold end of main heat exchanger 3 to produce a first liquid air stream 25.
• the liquid air stream 25 is then partially expanded in an expansion valve 45 and divided into liquid streams 46 and 48 for introduction into the distillation column system 5.
• second stream 22 is directed to a turbine based refrigeration circuit 4.
• Turbine based refrigeration circuits are often referred to as either a lower column turbine (LCT) arrangement or an upper column turbine (UCT) arrangement which are used to provide refrigeration to a two-column or three column cryogenic air distillation column system.
• LCT lower column turbine
• UCT upper column turbine
• a portion of the pre- purified, compressed feed air 18 is further compressed and partially cooled in the main or primary heat exchanger 3.
• stream 22 is further compressed by a turbine loaded booster compressor 26 and yet further compressed by a second booster compressor 28 to a pressure that can be in the range from between about 20 bar(a) to about 60 bar(a) to produce further compressed stream 30.
• Further compressed stream 30 is also directed or introduced into main heat exchanger 3 in which it is partially cooled to a temperature in a range of between about 160 and about 220 Kelvin to form a partially cooled stream 31 that is subsequently introduced into a turbo-expander 32 to produce an exhaust stream 34 that is introduced into the higher pressure column 52 of distillation column system 5.
• Turbo-expander 32 is preferably linked with booster compressor 26, either directly or by appropriate gearing.
• the turbine air circuit illustrated in Fig. 1 is shown as a lower column turbine (LCT) air circuit where the expanded exhaust stream is fed to the higher pressure column of the distillation column system, it is contemplated that the turbine based refrigeration circuit alternatively may be an upper column turbine (UCT) air circuit where the turbine exhaust stream is directed to the lower pressure column. Still further, the turbine air circuit may be combinations of LCT circuits and UCT circuits and/or even other variations of such known turbine air circuits such as a partial lower column turbine (PLCT).
• LCT lower column turbine
• UCT upper column turbine
• a portion of the purified and compressed feed air may be partially cooled in the primary heat exchanger, and then all or a portion of this partially cooled stream is diverted to a warm turbo-expander.
• the expanded gas stream or exhaust stream from the warm turbo-expander is then directed to the lower pressure column in the two-column or three column cryogenic air distillation column system.
• the cooling or supplemental refrigeration created by the expansion of the exhaust stream is thus imparted directly to the lower pressure column thereby alleviating some of the cooling duty of the main heat exchanger.
• the aforementioned components of the feed air streams namely oxygen, nitrogen, and argon are separated within the distillation column system 5 that consists of a higher pressure column 52 and a lower pressure column 54. It is understood that if argon were a necessary product, an argon column (not shown) could be incorporated into the distillation column system 5.
• the higher pressure column 52 typically operates in the range from between about 20 bar(a) to about 60 bar(a) whereas the lower pressure column 54 typically operates at pressures between about 1.1 bar(a) to about 1.5 bar(a).
• the higher pressure column 52 and the lower pressure column 54 are linked in a heat transfer relationship such that a nitrogen-rich vapor column overhead, extracted from the top of higher pressure column 52 as a stream 56, is condensed within a condenser-reboiler 57 located in the base of lower pressure column 54 against boiling an oxygen-rich liquid column bottoms 58.
• the boiling of oxygen-rich liquid column bottoms 58 initiates the formation of an ascending vapor phase within lower pressure column 54.
• the condensation produces a liquid nitrogen containing stream 60 that is divided into streams 62 and 64 that reflux the higher pressure column 52 and the lower pressure column 54, respectively to initiate the formation of descending liquid phases in such columns.
• Exhaust stream 34 is introduced into the higher pressure column 52 along with the liquid stream 46 for rectification by contacting an ascending vapor phase of such mixture within a plurality of mass transfer contacting elements, illustrated as contacting elements 66 and 68, with a descending liquid phase that is initiated by reflux stream 62.
• a stream 72 of the crude liquid oxygen column bottoms 70 is expanded in an expansion valve 74 to the pressure at or near that of the lower pressure column 54 and is introduced into the lower pressure column for further rectification.
• Second liquid stream 48 is passed through an expansion valve 76, expanded to the pressure at or near that of the lower pressure column 54 and then introduced into lower pressure column 54.
• Lower pressure column 54 is also provided with a plurality of mass transfer contacting elements, illustrated as contacting elements 78, 80, 82 and 84 that can be trays or structured packing or random packing or other known elements in the art of cryogenic air separation.
• the separation produces an oxygen-rich liquid 58 and a nitrogen-rich vapor column overhead that is extracted as a nitrogen product stream 86.
• a waste stream 88 is also extracted to control the purity of nitrogen product stream 86.
• Both nitrogen product stream 86 and waste stream 88 are passed through a subcooling unit 90 designed to subcool the reflux stream 64.
• a portion of the reflux stream 64 may optionally be taken as a liquid product stream 92 and the remaining portion (shown as stream 93) may be introduced into lower pressure column 54 after passing through expansion valve 94.
• nitrogen product stream 86 and waste stream 88 are fully warmed within main heat exchanger 3 to produce a warmed nitrogen product stream 95 and a warmed waste stream 96.
• the warmed waste stream 96 may be used to regenerate the adsorbents within prepurification unit 16.
• an oxygen-rich liquid stream 98 is extracted from the oxygen-rich liquid column bottoms 58 near the bottom of the lower pressure column 54. Oxygen-rich liquid stream 98 can be pumped by a pump 99 to form a pumped product stream as illustrated by pumped liquid oxygen stream 100.
• Part of the pumped liquid oxygen stream 100 can optionally be taken directly as a liquid oxygen product stream 102, with the remainder, namely stream 104, being directed to the main heat exchanger 3 where it is warmed and vaporized to produce a pressurized oxygen product stream 106.
• stream 104 Although only one such stream 104 is shown, there could be a plurality of such streams that are fed into the main heat exchanger 3.
• Pumped liquid oxygen stream 100 can be pressurized to above or below the critical pressure so that oxygen product stream 106 when discharged from the main heat exchanger 3 will be a supercritical fluid. Alternatively, the pressurization of pumped liquid oxygen stream 100 could be lower to produce an oxygen product stream 106 in a vapor form.
• the main heat exchanger 3 is preferably a brazed aluminum plate-fin type heat exchanger.
• Such heat exchangers are advantageous due to their compact design, high heat transfer rates and their ability to process multiple streams. They are manufactured as fully brazed and welded pressure vessels.
• the brazing operation involves stacking corrugated fins, parting sheets and end bars to form a core matrix. The matrix is placed in a vacuum brazing oven where it is heated and held at brazing temperature in a clean vacuum environment.
• a heat exchanger comprising a single core may be sufficient.
• a heat exchanger may be constructed from several cores which must be connected in parallel or series.
• air separation plant 1 is capable of producing liquid products, namely, nitrogen-rich liquid stream 92 and liquid oxygen product stream 102.
• additional refrigeration is supplied by a supplemental refrigeration circuit 7.
• the present system the present system, the supplemental refrigeration circuit 7.
• supplemental refrigeration circuit 7 is preferably added to the cryogenic air separation plant 1 after initial plant construction.
• the design of the supplemental refrigeration circuit 7 is tailored for such late add-on or retrofit application and the tie-in points to the cryogenic air separation plant 1 are minimized.
• the first tie-in point 100 preferably occurs downstream of the main air compression train 2 where a portion of the compressed and purified feed air stream is diverted as third stream 1 10.
• This diverted third stream 1 10 provides a base volume of refrigerant for the supplemental refrigeration circuit 7.
• the second tie-in point 200 is within the booster air compression circuit 6 or turbine based refrigeration circuit 4 and is configured to divert a portion of the further compressed stream 30 upstream of the main heat exchanger as stream 156 to an auxiliary heat exchanger 180 in the supplemental refrigeration circuit 7 where it is cooled by the refrigerant stream 152.
• the cooled stream 158 is then returned to the turbine based refrigeration circuit 4 at the third tie-in point 300 downstream of the main heat exchanger 3.
• the selected tie-in points avoid changes to the main heat exchanger 3 and distillation column systems.
• the closed loop supplemental refrigeration circuit 7 uses a compressible working fluid or refrigerant such as air which is compressed in a multi-stage compression section 1 15.
• the working fluid or refrigerant stream 114 within the closed loop supplemental refrigeration circuit 7 is compressed in a first compressor 1 16 and then fed to a second booster compressor 1 18 coupled to a turbo-expander 124.
• the compressed working fluid or refrigerant stream 122 may then be cooled using an aftercooler 120 to remove the heat of compression prior to expansion in turbo-expander 124.
• the aftercooler 120 cools the compressed working fluid stream 122 to ambient or a chilled temperature by means of chilled water or other refrigeration source associated with the air separation plant. Such aftercooling generally improves cycle efficiency and prevents damage to the turbo-expander 124 due to high temperatures.
• the turbo-expander 124 is configured to expand the compressed working fluid stream 122 to generate a cooled working fluid stream 152.
• the cooled working fluid stream 152 is then warmed in the auxiliary heat exchanger 180 so as to impart a portion of the refrigeration required by the air separation plant 1 required to produce the nitrogen and oxygen liquid product streams 92 and 102.
• the warmed working fluid stream 154 is recirculated back to the compressor section 1 15 after having passed through the auxiliary heat exchanger 180.
• the turbo-expander 124 is preferably linked with booster compressor 118, either directly or by appropriate gearing.
• the turbo-expander may to be connected or operatively coupled to a generator.
• Such generator loaded turbo-expander arrangement allows the speed of the turbo-expander to be maintained constant even at very high or low loads. This arrangement is desirable in some applications because the speed of the turbo- expander would remain generally constant at the ideal efficiency across the entire operating envelope and the control methods of the turbo-expander, as discussed in more detail below, would be further simplified.
• the generator load may be connected to the turbo-expander by means of a high speed generator.
• the generator load may be connected to the turbo-expander by means of a high speed coupling connected to an internal or external gearbox and with a low speed coupling from the gearbox to the generator.
• the operation and control of the supplemental refrigeration circuit should be controlled to avoid cycling of the compressors and turbo-expanders between operating mode or On' mode where additional liquid product is needed and shut-down or Off mode when the supplemental refrigeration is not required. Such cycling adversely impacts the overall efficiency and reliability of the supplemental refrigeration cycle. Rather, the supplemental refrigeration circuit should be capable of rum down so as to provide less supplemental refrigeration, but without completely shutting down when less liquid product is needed.
• the source of the working fluid or refrigerant stream 114 is preferably a portion of the compressed and purified feed air stream 18, diverted as charge stream 110 to the supplemental refrigeration circuit 7 upstream of the compressor 116.
• Working fluid or refrigerant may be added via one or more inlet valves 112 and 142 operatively disposed upstream of the compressor 116 of the supplemental refrigeration circuit 7 that are open and closed, as required, to maintain a substantially constant volumetric flow rate of the working fluid through the compressors 116, 118 and turbo- expander 124 and a substantially constant pressure ratio across the compressor section 115.
• Inlet valves 112 and 142 are controllably operated to set the inlet pressure of the compressor 116 and hence outlet pressure of the turbo-expander 124.
• Inlet valve 1 12 is preferably larger of the two inlet valves and is used to charge or pressurize the supplemental refrigeration circuit or opened when rapid change in the inlet pressure is needed whereas inlet valve 142 provides continuing adjustment to the pressure in the supplemental refrigeration circuit 7. In this manner, increasing the inlet pressure in the supplemental refrigeration circuit 7 can increase the power provided by equipment and hence the refrigeration imparted to the auxiliary heat exchanger 180 and back to the cryogenic air separation plant 1 thereby allowing for a higher liquid make rate.
• working fluid to may be added to the supplemental refrigeration circuit 7 by means of a low pressure make-up supply of refrigerant provided via valve 143 upstream of the compressor 1 16 to maintain a minimum pressure in the supplemental refrigeration circuit 7.
• valve 143 will open if a minimum pressure in the supplemental refrigeration circuit 7 is not maintained, as may occur during typical shutdown operation.
• the supplemental refrigeration circuit 7 also includes a vent system 140 comprising a valve 144 and vent 145 disposed upstream of the turbo-expander 124.
• the vent system 140 is configured to removing a portion of the working fluid or refrigerant in the supplemental refrigeration circuit 7 when the pressure is above the desired or targeted pressure so as to maintain the substantially constant volumetric flow rate and
• An auxiliary vent arrangement including valves 146, 147 and vent 148 are optionally disposed downstream of the turbo-expander 124 and upstream of the auxiliary heat exchanger 180 that typically opens during startup.
• a supplemental refrigeration circuit controller (not shown) to add or remove working fluid
• the controller is preferably a master PLC type control unit operatively connected to local PID controllers (not shown) that control the vent system valve 144, and inlet valves 1 12, 142 to adjust or control the removal or addition of working fluid in the supplemental refrigeration circuit 7 while maintaining a substantially constant volumetric flow rate of the working fluid through compressor and turbo-expander sections of the supplemental refrigeration circuit and a substantially constant pressure ratio across the compressor section.
• the supplemental refrigeration circuit controller can be a manual or operator based controller.
• Adjusting the setpoints for the vent system valve 144 and/or inlet valves 112, 142 changes the inlet pressure to the supplemental refrigeration circuit 7 and as indicated above, either: (i) increases the supplemental refrigeration and thereby increases liquid product make rate in the air separation plant 1 ; or (ii) decreases supplemental refrigeration and thereby decreases the liquid product make rate in the air separation plant 1.
• supplemental refrigeration circuit controller or other suitable control means may be configured to also control the adjustments to the inlet guidevanes
• Adjustments of the turbine nozzles 125 are controlled to maintain substantially constant volumetric flow rates over wide pressure variations.
• the turbine nozzles 125 are also adjusted to keep the pressure ratio over the turbo-expander 124 generally constant.
• Adjustment of the compressor inlet guidevanes 1 17 on one or both of the compressors 116, 1 18 helps maintain the substantially constant pressure ratio across the compressors, and more particularly, makes necessary adjustments to correct for effects such as compressibility of the working fluid, changes in inlet temperature and mismatches with the turbine nozzles 125.
• the preferred method of operating an air separation plant with the disclosed supplemental refrigeration circuit comprises the steps of : (i) conducting a cryogenic rectification process in an air separation plant to produce liquid nitrogen and/or liquid oxygen; (ii) diverting a portion of the compressed and purified feed air stream to the supplemental refrigeration circuit as the refrigerant or working fluid; (iii) producing a portion of the refrigeration required by the air separation plant by compressing and subsequently expanding (and thereby cooling) the refrigerant or working fluid in the supplemental refrigeration circuit, as described above; (iv) warming the expanded and cooled refrigerant or working fluid in the auxiliary heat exchanger via indirect heat exchange with a further compressed air stream diverted from the boosted air compression circuit or turbine based refrigeration circuit of the cryogenic air separation plant; (v) returning the cooled further compressed air stream from the auxiliary heat exchanger to the turbine based refrigeration circuit of the cryogenic air separation plant; (vi) recirculating the warmed working fluid back through the supplemental refrigeration circuit to the compression section of the supplemental refrigeration
• Adjusting the inlet guidevanes in the compressors in the supplemental refrigeration circuit and/or the turbine nozzles in the turbo-expander in the supplemental refrigeration circuit optimizes the pressure ratios and constant volume flows, respectively. Adding the additional mass flow of the refrigerant or working fluid ultimately allows for the increase in the supplemental refrigeration and thereby allows for increasing the liquid product make rate in the air separation plant. Conversely, removing the refrigerant or working fluid generally decreases the supplemental refrigeration and thereby decreases the liquid product make rate in the cryogenic air separation plant.

Landscapes

• Engineering & Computer Science (AREA)
• Physics & Mathematics (AREA)
• Mechanical Engineering (AREA)
• Thermal Sciences (AREA)
• General Engineering & Computer Science (AREA)
• Health & Medical Sciences (AREA)
• Emergency Medicine (AREA)
• Separation By Low-Temperature Treatments (AREA)

Priority Applications (5)

Applications Claiming Priority (2)

Publications (1)

Family

ID=57208389

Family Applications (1)

Country Status (7)

Families Citing this family (5)

Citations (4)

Family Cites Families (2)

• 2015
  • 2015-11-09 US US14/935,680 patent/US10018412B2/en active Active
• 2016
  • 2016-10-18 KR KR1020187013746A patent/KR102110699B1/ko active IP Right Grant
  • 2016-10-18 MX MX2018005454A patent/MX2018005454A/es unknown
  • 2016-10-18 CN CN201680064205.3A patent/CN108351165B/zh active Active
  • 2016-10-18 CA CA3004415A patent/CA3004415C/en active Active
  • 2016-10-18 EP EP16787986.5A patent/EP3374713A1/en active Pending
  • 2016-10-18 WO PCT/US2016/057465 patent/WO2017083062A1/en active Application Filing

Patent Citations (4)

Also Published As

Similar Documents

Legal Events